CN113228213A

CN113228213A - Separator for aluminum electrolytic capacitor and aluminum electrolytic capacitor

Info

Publication number: CN113228213A
Application number: CN201980085680.2A
Authority: CN
Inventors: 越智贵史; 石休正树; 熊冈弘伦
Original assignee: Nippon Kodoshi Corp
Current assignee: Nippon Kodoshi Corp
Priority date: 2018-12-27
Filing date: 2019-12-17
Publication date: 2021-08-06
Anticipated expiration: 2039-12-17
Also published as: US20220230814A1; TWI828822B; EP3905289A4; WO2020137675A1; BR112021012564A2; CN113228213B; EP3905289A1; JP6827458B2; KR20210105910A; JP2020107769A; TW202032594A

Abstract

The purpose of the present invention is to provide a separator for an aluminum electrolytic capacitor and an aluminum electrolytic capacitor, which improve the uniformity of a conductive polymer in a solid electrolytic capacitor or a hybrid electrolytic capacitor and achieve a further reduction in ESR of the capacitor. The present invention has the following technical features as one means for achieving the object. A separator for an aluminum electrolytic capacitor, wherein the separator is interposed between a pair of electrodes, and wherein the impregnation rate at which the bottom surface of an element obtained by winding the separator interposed between the pair of electrodes is immersed in an electrolyte solution is 50 seconds or less. Further, an aluminum electrolytic capacitor including a pair of electrodes with the separator interposed therebetween is characterized by using the separator. Further, the pair of electrodes is characterized in that a conductive polymer is used as a cathode material.

Description

Separator for aluminum electrolytic capacitor and aluminum electrolytic capacitor

Technical Field

The present invention relates to a separator for an aluminum electrolytic capacitor interposed between a pair of electrodes, and an aluminum electrolytic capacitor using the separator for an aluminum electrolytic capacitor.

Background

Aluminum electrolytic capacitors are used in many fields such as automotive electronic components and electronic devices. Among aluminum electrolytic capacitors, aluminum solid electrolytic capacitors (hereinafter referred to as "solid electrolytic capacitors") using a conductive polymer as a cathode material and conductive polymer-mixed aluminum electrolytic capacitors (hereinafter referred to as "mixed electrolytic capacitors") using a conductive polymer and an electrolyte as a cathode material have a smaller equivalent series resistance (hereinafter referred to as "ESR") than ordinary aluminum electrolytic capacitors using only an electrolyte as a cathode material, and thus the range of applications thereof is expanded.

A typical solid electrolytic capacitor is fabricated as follows: a separator is interposed between an anode aluminum foil and a cathode aluminum foil, the anode aluminum foil and the cathode aluminum foil are wound, a polymerization liquid impregnated with a conductive polymer is polymerized to obtain an element containing a conductive polymer, and the element is inserted into a case and sealed to produce a solid electrolytic capacitor. A separator is interposed between the anode aluminum foil and the cathode aluminum foil, the anode aluminum foil and the cathode aluminum foil are wound, the conductive polymer dispersion is impregnated with the conductive polymer dispersion, and the resultant is dried to obtain an element containing a conductive polymer, and the element is inserted into a case and sealed to produce a solid electrolytic capacitor.

The hybrid electrolytic capacitor is manufactured as follows: the element containing a conductive polymer is further impregnated with an electrolytic solution, inserted into a case, and sealed to produce a hybrid electrolytic capacitor.

A conduction mechanism of a general aluminum electrolytic capacitor using only an electrolytic solution is ion conduction, and a conduction mechanism of a solid electrolytic capacitor or a hybrid electrolytic capacitor containing a conductive polymer is electron conduction. Therefore, solid electrolytic capacitors and hybrid electrolytic capacitors have higher response and lower ESR than ordinary aluminum electrolytic capacitors.

Separators used in solid electrolytic capacitors and hybrid electrolytic capacitors are required to isolate the electrodes from each other, prevent short-circuit defects, and retain conductive polymers.

Heretofore, as separators for solid electrolytic capacitors and hybrid electrolytic capacitors, for example, techniques described in patent documents 1 to 3 have been disclosed.

The separator described in patent document 1 is a separator containing fibers made of a semi-aromatic polyamide resin and having good compatibility with a conductive polymer, and by using the separator, the retention of an electrolyte is improved, and the ESR characteristics of a solid electrolytic capacitor can be improved.

The separator of patent document 2 is a separator containing a non-fibrillated organic fiber or a fibrillated polymer and having a high water absorption rate, and a technique of reducing the ESR of a solid electrolytic capacitor by using the separator is disclosed.

The separator of patent document 3 is a separator that improves the compression impregnation rate of the separator. By using the separator, ESR of the solid electrolytic capacitor is reduced, and electrostatic capacitance can be improved.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2004-165593

Patent document 2: japanese patent laid-open No. 2004-235293

Patent document 3: japanese patent No. 6411620

The separator of patent document 1 is a separator containing fibers made of a semi-aromatic polyamide resin and having good compatibility with a conductive polymer, and by using the separator, the retention of an electrolyte is improved, and the ESR characteristics of a solid electrolytic capacitor can be improved.

Disclosure of Invention

Problems to be solved by the invention

Capacitors including solid electrolytic capacitors, hybrid electrolytic capacitors have always been required to have a reduced ESR and an improved electrostatic capacitance. However, even when the separators of patent documents 1 to 3 are used, it is difficult to reduce ESR by a certain level or more in the solid electrolytic capacitor and the hybrid electrolytic capacitor. This is considered to be mainly for the following reason.

In the conventional separators having a high water absorption rate as in patent documents 2 and 3, the polymerization liquid or dispersion of the conductive polymer has good liquid absorption properties of the solvent or dispersion medium, but the impregnation properties of the conductive polymer itself are not necessarily good. This is because, when the electrode foil and the separator are wound and impregnated with the polymer liquid or dispersion of the conductive polymer, the solvent or dispersion medium of the polymer liquid or dispersion of the conductive polymer may not be impregnated with the solute or the dispersoid, as in the case of paper chromatography.

Further, when the solvent (dispersion medium) and the solute (dispersoid) are separated from each other in this way, the conductive polymer is unevenly distributed in the capacitor, and the uniformity of the conductive polymer is reduced.

In addition, in the case of the separator having good compatibility with the conductive polymer as in patent document 1, although separation between the solvent (dispersion medium) and the solute (dispersoid) is not easily caused, impregnation itself of the polymerization liquid or dispersion of the conductive polymer having a high-viscosity liquid is difficult, and there is a possibility that uneven distribution of the conductive polymer in the capacitor element is caused.

As a result of various studies, the present inventors have found that, in a solid electrolytic capacitor, before polymerization of a conductive polymer polymerization liquid and before drying of a conductive polymer dispersion, the amount of liquid held is unevenly distributed in the capacitor element, and the conductive polymer after polymerization and drying is also uneven, and therefore, the ESR cannot be reduced.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a separator for an aluminum electrolytic capacitor and an aluminum electrolytic capacitor, which improve the uniformity of a conductive polymer in a solid electrolytic capacitor or a hybrid electrolytic capacitor and achieve a further reduction in ESR of the capacitor.

Means for solving the problems

In order to achieve the above object, a capacitor for an aluminum electrolytic capacitor according to the present invention has the following technical features, for example.

That is, the separator for an aluminum electrolytic capacitor is interposed between a pair of electrodes, and the impregnation rate at which the bottom surface of an element obtained by winding the separator interposed between the pair of electrodes is immersed in an electrolytic solution is 50 seconds or less.

The aluminum electrolytic capacitor is characterized by comprising a pair of electrodes and a separator interposed between the pair of electrodes, and the separator is used.

An aluminum electrolytic capacitor is characterized in that a conductive polymer is used as a cathode material in the pair of electrodes.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a separator for an aluminum electrolytic capacitor and an aluminum electrolytic capacitor having reduced ESR can be provided.

Detailed Description

An embodiment of the present invention will be described in detail below.

The separator of the present embodiment is a separator having an impregnation rate of 50 seconds or less. The impregnation rate in the present embodiment is a time until the bottom surface of the element having a diameter of 6mm and a height of 18mm, which is obtained by winding the anode foil and the cathode foil with the separator interposed therebetween, is immersed in the electrolyte until the electrostatic capacitance measured at 120Hz and 20 ℃ by an LCR meter becomes 90% or more of the rated electrostatic capacitance.

In this embodiment, a 25 mass% γ -butyrolactone solution of imidazolium phthalate was used for an element obtained by winding an anode foil 15mm wide and 100 μm thick and a cathode foil 15mm wide and 50 μm thick with a separator 18mm wide interposed therebetween, and the time until the electrostatic capacitance became 90% or more of the rated electrostatic capacitance was measured.

When the wound element has a size of 6mm in diameter and 18mm in height, the width and thickness of the anode foil and the cathode foil are not particularly limited. The electrolyte used in the electrolytic solution is not limited to the imidazolium phthalate, and an imidazolium salt modified with an ethyl group or a methyl group, an imidazolium salt with a double bond cleaved, or other dicarboxylic acid salts may be used.

The impregnation rate of the present embodiment is not the impregnation of the separator alone, but the impregnation after the element formation is directly measured, and the impregnation in the actual manufacturing process of the capacitor can be directly measured.

By setting the impregnation rate of the separator to 50 seconds or less, the impregnation and holding properties of the conductive polymer are improved, and the ESR of the capacitor can be reduced.

When the impregnation rate exceeds 50 seconds, the impregnation property is deteriorated, and the amount of the conductive polymer held in the capacitor element is unevenly distributed, and there is a possibility that the ESR cannot be reduced. Further, when the electrolyte solution is used in a hybrid electrolytic capacitor, the electrolyte solution has low retentivity, and therefore, when the hybrid electrolytic capacitor is used, the electrolyte solution drops in the direction of gravity, and the electrostatic capacitance may decrease.

The faster the impregnation rate, the better the impregnation rate, but less than 5 seconds is difficult in view of the handleability of the separator, and the lower limit is about 5 seconds.

The separator of the present embodiment is not particularly limited in terms of the fibers used for the separator, provided that the separator satisfies the impregnation rate and has sufficient strength and chemical resistance as a separator for a solid electrolytic capacitor or a hybrid electrolytic capacitor.

Examples of the fibers used in the separator of the present embodiment include cellulose fibers and synthetic fibers.

The cellulose fiber includes natural cellulose fiber and regenerated cellulose fiber, and can be used without particular limitation. The cellulose fibers may be those obtained by purifying natural cellulose fibers or those obtained by alkalizing natural cellulose fibers with cellulose. As the natural cellulose fiber, there are abaca, sisal, jute, kenaf, cotton linter, esparto grass, coniferous tree, broadleaf tree, and the like, but not limited thereto. The cellulose fibers may be pulped as long as they can satisfy the impregnation speed of 5 to 50 seconds.

Examples of the synthetic fibers include nylon fibers, polyester fibers, acrylic fibers, and aramid fibers, and they may be used without particular limitation. The fibers may be fibrillated fibers or non-fibrillated fibers, and these fibers may be used in combination. Among them, nylon fibers are preferable from the viewpoint of affinity with the polymerization liquid or dispersion of the conductive polymer.

The cellulose fiber has good affinity with the solvent of the polymerization liquid or dispersion of the conductive polymer, and has a high impregnation rate, and the retention of the polymerization liquid or dispersion of the conductive polymer is easily improved. The synthetic fibers are easily formed into a bulky sheet, and the impregnation speed can be increased. Further, since synthetic fibers are also more resistant to chemical agents than cellulose, polymerization of the conductive polymer is not inhibited, and deterioration due to a polymerization solution or dispersion of the conductive polymer is small.

For example, the impregnation speed of the separator can be satisfied by using cellulose fibers having an average fiber length of 0.5 to 2.0mm and synthetic fibers having no fibrillation.

However, the impregnation rate range in the present embodiment is not limited to the cellulose fibers having the average fiber length and the synthetic fibers having no fibrillation. For example, cellulose fibers and fibrillated synthetic fibers having an average fiber length of 0.4mm can be used by reducing the content of these fibers in the separator.

The thickness and density of the separator in the present embodiment are not particularly limited. Considering strength and handling property in use, the thickness is usually 20 to 100 μm, and the density is usually 0.20 to 0.60g/cm³Degree of the disease.

In the embodiment of the present invention, the separator is a wet nonwoven fabric formed by a papermaking method. The paper-making form of the separator is not particularly limited as long as the impregnation rate can be satisfied, and paper-making forms such as fourdrinier paper, short wire paper, and cylinder paper can be used, and layers formed by these paper-making methods may be combined in multiple layers.

In addition, additives such as a dispersant, a defoaming agent, and a paper strength enhancer may be added to the separator for a capacitor to such an extent that the impurity content does not affect the separator for a capacitor during paper making.

Further, after the paper layer is formed, paper strengthening processing, lyophilic processing, calendering processing, embossing processing, and the like may be performed.

In the aluminum electrolytic capacitor of the present embodiment, the separator having the above-described structure is used as a separator, and a conductive polymer is used as a cathode material with the separator interposed between a pair of electrodes.

[ measuring method of characteristics of separator and aluminum electrolytic capacitor ]

The specific measurement of the characteristics of the separator and the aluminum electrolytic capacitor according to the present embodiment is performed under the following conditions and methods.

[ thickness ]

"JIS C2300-2" cellulose paper for electric use — part 2: the thickness of the separator was measured by a method of folding 10 sheets in the case of "the thickness was measured by folding the paper by 5.1.3" using a micrometer in the case of "the 5.1.1 measuring instrument and the measuring method a" defined in the test method "5.1 thickness".

[ Density ]

The paper was produced by using "JIS C2300-2" cellulose paper for electric use-part 2: test method 7.0 density "the density of the separator in an oven-dried state was measured by the method specified in method B.

[ speed of impregnation ]

An anode foil having a width of 15mm and a thickness of 100 μm and a cathode foil having a width of 15mm and a thickness of 50 μm were wound with a separator having a width of 18mm interposed therebetween, and the bottom surface of the obtained element having a diameter of 6mm and a height of 18mm was immersed in a 25 mass% γ -butyrolactone solution of 1-ethyl-2, 3-dimethyl-4, 5-dihydroimidazolium salt (hydrogen-phthalate), and the time until the electrostatic capacitance measured at 120Hz and 20 ℃ using an LCR meter was 90% or more of the rated electrostatic capacitance was measured.

[ average fiber length ]

The average fiber length was measured according to JIS P8226-2 "pulp-method for measuring fiber length by automatic analysis using optics" section 2: the value of the length-loaded average fiber length of the resulting Contourlength (straight length) (center line fiber length) was measured by the non-polarizing method (ISO16065-2 "Pulps-Determination of fiber length by automated optical analysis-Part 2: Un-polarized light method) using Kajaani fiber Ver.4 (manufactured by the company Kaso Automation).

[ESR]

The ESR of the capacitor thus produced was measured at 20 ℃ and 100kHz using an LCR meter.

[ Electrostatic capacitance ]

The electrostatic capacitance of the capacitor thus produced was measured by an LCR meter under conditions of a temperature of 20 ℃ and a frequency of 120 Hz.

[ Capacity maintenance Rate ]

The capacitance maintenance ratio was measured only for the hybrid electrolytic capacitor.

The electrostatic capacitance of the hybrid electrolytic capacitor after 5 minutes of centrifugal separation at a centrifugal acceleration of 1000G using a centrifugal separator was divided by the electrostatic capacitance before centrifugal separation to obtain a percentage.

[ production of solid electrolytic capacitor and hybrid electrolytic capacitor ]

After winding an anode foil and a cathode foil with a separator interposed therebetween and chemical conversion treatment, a capacitor element was impregnated with the conductive polymer dispersion, dried, inserted into a case, and sealed to produce a solid electrolytic capacitor having a rated voltage of 50V, a diameter of 8.0mm, and a height of 10.0 mm.

A hybrid electrolytic capacitor having a rated voltage of 80V and a diameter of 8.0mm × a height of 10.0mm was produced in the same manner as the solid electrolytic capacitor except that the hybrid electrolytic capacitor was impregnated with the electrolyte solution before being inserted into the case.

Specific examples, comparative examples, and conventional examples of the solid electrolytic capacitor and the hybrid electrolytic capacitor according to the embodiment of the present invention will be described in detail below.

[ example 1]

The separator of example 1 was obtained by mixing 15 mass% of linter pulp, 25 mass% of jute pulp, and 35 mass% of nylon fiber and performing cylinder papermaking.

The cellulose fibers of the separator had an average fiber length of 1.2mm, a thickness of 60 μm and a density of 0.55g/cm³The impregnation rate was 49 seconds.

[ example 2]

The cellulose-alkalized bamboo pulp 30 mass%, the sisal pulp 15 mass%, and the nylon fiber 55 mass% were mixed, and the mixture was subjected to cylinder papermaking to obtain the separator of example 2.

The cellulose fibers of the separator had an average fiber length of 1.3mm, a thickness of 20 μm and a density of 0.40g/cm³The impregnation rate was 38 seconds.

[ example 3]

30% by mass of cotton pulp, 30% by mass of a beating solvent spun rayon fiber, and 40% by mass of an unbaked rayon fiber having a fiber length of 4mm were mixed, and a cylinder paper was made to obtain the separator of example 3.

The cellulose fibers of the separator had an average fiber length of 2.4mm, a thickness of 90 μm and a density of 0.35g/cm³The impregnation rate was 12 seconds.

[ example 4]

The separator of example 4 was obtained by mixing 10 mass% of cotton pulp, 10 mass% of hemp pulp, and 80 mass% of acrylic fiber and performing cylinder papermaking.

The cellulose fibers of the separator had an average fiber length of 1.1mm and a thickness of40 μm, density 0.22g/cm³The impregnation rate was 5 seconds.

[ reference example ]

The separator of the reference example was obtained by mixing 20 mass% of cotton pulp, 40 mass% of polyester fiber, and 40 mass% of acrylic fiber, and performing cylinder papermaking.

The cellulose fibers of the separator had an average fiber length of 1.4mm, a thickness of 40 μm and a density of 0.17g/cm³The impregnation rate was 2 seconds.

[ comparative example ]

The separator of the comparative example was obtained by mixing 60 mass% of manila hemp pulp and 40 mass% of sisal hemp pulp and performing rotary screen printing.

The cellulose fibers of the separator had an average fiber length of 2.3mm, a thickness of 30 μm and a density of 0.65g/cm³The impregnation rate was 55 seconds.

[ conventional example 1]

Referring to example 3 of patent document 2, a separator of conventional example 1 was obtained by mixing 5 mass% of cotton pulp, 30 mass% of fibrillated aramid fiber, and 65 mass% of polyester fiber and performing cylinder papermaking.

The cellulose fibers of the separator had an average fiber length of 0.4mm, a thickness of 45 μm and a density of 0.38g/cm³The impregnation rate was 61 seconds.

[ conventional example 2]

Referring to example 7 of patent document 3, a separator of conventional example 2 was obtained by mixing 30% by mass of cotton pulp, 30% by mass of manila hemp pulp, and 40% by mass of fibrillated acrylic fiber and performing cylinder papermaking.

The cellulose fibers of the separator had an average fiber length of 2.1mm, a thickness of 35 μm and a density of 0.28g/cm³The impregnation rate was 54 seconds.

Solid electrolytic capacitors and hybrid electrolytic capacitors were produced as the aluminum electrolytic capacitors produced using the separators of the above examples, reference examples, comparative examples, and conventional examples.

The following description will be made of a solid electrolytic capacitor and a hybrid electrolytic capacitor using separators of examples, reference examples, comparative examples, and conventional examples.

[ example 1]

The solid electrolytic capacitor using the separator of example 1 had a capacitance of 48 μ F, ESR of 26m Ω. The hybrid electrolytic capacitor using the separator of example 1 had a capacitance of 40 μ F, a volume retention rate of 91%, and an ESR of 32m Ω.

[ example 2]

The solid electrolytic capacitor using the separator of example 2 had a capacitance of 47 μ F, ESR of 26m Ω. The hybrid electrolytic capacitor using the separator of example 2 had a capacitance of 40 μ F, a volume retention rate of 93%, and an ESR of 33m Ω.

[ example 3]

The solid electrolytic capacitor using the separator of example 3 had an electrostatic capacitance of 45 μ F, ESR of 28m Ω. The hybrid electrolytic capacitor using the separator of example 3 had a capacitance of 37 μ F, a volume retention rate of 95%, and an ESR of 35m Ω.

[ example 4]

The solid electrolytic capacitor using the separator of example 4 had an electrostatic capacitance of 44 μ F, ESR of 29m Ω. The hybrid electrolytic capacitor using the separator of example 4 had a capacitance of 36 μ F, a volume retention rate of 96%, and an ESR of 36m Ω.

[ reference example ]

The separator of the reference example was used to fabricate a capacitor element, but the strength was weak, and the separator was broken frequently during the fabrication of the element, so that the capacitor element could not be fabricated by either the solid electrolytic capacitor or the hybrid electrolytic capacitor.

[ comparative example ]

The solid electrolytic capacitor using the separator of the comparative example had an electrostatic capacitance of 38 μ F, ESR of 40m Ω. The hybrid electrolytic capacitor using the separator of the comparative example had a capacitance of 28 μ F, a volume retention rate of 80%, and an ESR of 45m Ω.

[ conventional example 1]

The solid electrolytic capacitor using the separator of conventional example 1 had a capacitance of 40 μ F, ESR of 37m Ω. The hybrid electrolytic capacitor using the separator of conventional example 1 had a capacitance of 29 μ F, a volume retention rate of 82%, and an ESR of 40m Ω.

[ conventional example 2]

The solid electrolytic capacitor using the separator of conventional example 2 had a capacitance of 55 μ F, ESR of 33m Ω. The hybrid electrolytic capacitor using the separator of conventional example 2 had a capacitance of 32 μ F, a volume retention rate of 86%, and an ESR of 32m Ω.

[ Table 1]

The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separators of the examples have improved electrostatic capacitance by 10% or more and reduced ESR by 10% or more, as compared with the solid electrolytic capacitor and the hybrid electrolytic capacitor of the conventional example. The capacity retention rate of the hybrid electrolytic capacitors of the examples was also good, being 90% or more.

As is clear from comparison of the examples, reference examples, comparative examples, and conventional examples, when the impregnation rate of the separator is 50 seconds or less, the electrostatic capacity and ESR of the solid electrolytic capacitor and the hybrid electrolytic capacitor are improved, and the capacity retention rate of the hybrid electrolytic capacitor can also be improved.

As described above, according to the embodiment of the present invention, since the impregnation speed of the conductive polymer is high, the holding property is also high, and there is no decrease in the retention property with time, the uneven distribution of the holding amount of the liquid in the capacitor element can be suppressed before the polymerization of the conductive polymer polymerization liquid and before the drying of the conductive polymer dispersion, and the ESR of the capacitor can be reduced.

Further, when the separator is used in a hybrid electrolytic capacitor, the retention of the electrolytic solution is also good, and there is no deterioration in the retention over time, so that when the hybrid electrolytic capacitor is used, the reduction in the electrostatic capacitance due to the electrolytic solution falling in the direction of gravity can be suppressed.

Claims

1. A separator for an aluminum electrolytic capacitor, which is interposed between a pair of electrodes,

the impregnation rate of the bottom surface of the element obtained by winding the separator with the separator interposed between the pair of electrodes in the electrolytic solution is 50 seconds or less.

2. An aluminum electrolytic capacitor comprising a pair of electrodes with a separator interposed therebetween, wherein the separator according to claim 1 is used.

3. The aluminum electrolytic capacitor according to claim 2, wherein a conductive polymer is used as a cathode material in the pair of electrodes.